[RodB]

Richard, I'm using black, as the common and purple. Blue is the lower impedance at 5K and purple is the higher at 10K. They seem to work equally, although I haven't pushed a signal through the tube to measure which one produces the most output. I did it by ear. The speaker output wires are the 2 that are the same color coming from the same side of the transformer. One transformer I have they are pink and the other they are black. If in doubt measure the resistance, should be around 2-3 ohms. I have used this transformer at least six times and it has worked well. There's another one that's identical except it handles a little more power for those 6L6s and EL84s, the Bogen T-72510.